Heat responsive electric switch



Feb. 20, 1951 P. BAL-:RTL

HEAT RESPONSIVE ELECTRIC SWITCH Filed NOV. 20, 1948 Snventof PAUL BAERTL .llllllllllll nnnnnnnnnnn a.

Patented Feb. 20, `i951 UNITED kSTATES PATENT OFFICE Application November 20, 1948, Serial No.16'1,165

y In Switzerland December 22, 1947 f 4 claims. (o1. 20c- 142) This invention relates to an electrical contact maker applicable in devices for the disclosure of temperature raising, comprising a movable contact member submitted to the force of a spring and a fixed contact member.

According the'invention, between such contact members a replaceable insulating part is provided consisting of a nonconductive material, capable of melting at temperature raising.

This insulating part may consist of paraffin, stearin, wax or of a mixture of two or three of these substances. Preferably this fusible material is mounted on a support consisting of conductive material and may be inserted or arranged between the contact members. The contact maker may be contained in a tube or casing provided with connecting terminals or may be disposed on a part in form of a cane or a rod, particularly if the device is destined for haystacks, in which case the cane or rod is put into the hay. Preferably the contact maker is connected to a source of electric current and to optic or acoustic signal means. If the contact maker comprises several contacts, these contacts may be arranged in series or in parallel.

The device functions as follows:

By attaining a predetermined temperature, in a haystack for instance the insulating part melts, permitting the two contact members to make contact and therefore to close an electric circuit. If the insulating part consists of a layer of fusible material coating a metallic support, which is particularly convenient if the insulating part is to be easily replaced, the support forms a bridge between the two connecting terminalsl of the circuit. Preferably one of the connecting terminals is mounted in a suitable manner to be removed, in order to facilitate the replacement of the insulating part.

The accompanying drawing shows by way of example one form of a contact maker of the present invention, which is not limited to the exact construction shown.

In the drawing,

Fig. l is a sectional View of a connecting terminal of the contact maker,

Fig. 2 is an axial section of a part of the device with a connecting nipple.

Fig. 3 is an enlarged cross section of one of the parts shown in Figs. 1 or 2.

Referring to the drawings the device comprises parts or elements of Fig. l and one element of Fig. 2 for special purposes.

The element consists of a tube I, which, in the case of Fig. 1, is provided with a point 2.

Other elements (Fig. l) are provided on both ends with threads 3 on the outer side, permitting the connection of a desired number of such elements by means of nipples 4. Two strips 5 of semi-circular cross section are arranged within the tubes I. The outer surface of such strips is coated with a layer 6 of insulating material having a predetermined melting point. In the center oi the tubes I a metal rod 'I is disposed, which rod is slitted over a part of its length, forming two outwardly curved halves 8, abutting like springs against the strips 5 and pressing the insulating layer 6 against the inner surface of tube I.

The ends 9 of the rods 'I are fixed in a bore I of a base II and sleeve I2 of insulating material, pressed into the ends of the tubes I. The ends I3 of the rods I protrude from the sleeves I2 to make electric contact when two elements are connected by a nipple 4.

Thus the tubes I of the elements are connected electrically by means of the nipples 4 and the rods 'I make contact at the contacting ends I3.

To lead voltage to the tubes I and rods 'I respectively a nipple I4 is screwed on to the thread 3 of the first element. A central portion I5 of insulating material is provided on this nipple I4. Within this portion I5 a contact socket I6 is disposed for receiving a plug. A projection I'I of the socket I6 makes contact with the front side I8 of the end 9 of a rod 'I.

A source of current I9 delivers the voltage. The circuit comprises an acoustic signal 20 and is completed by a lead 2|, a plug 22 and a plug 23 to be inserted into a Ybore 24 of the nipple I4.

In place of sockets and plugs, screws and nuts may be provided on the nipple I4 to connect the source of current I9 with the contact maker constituted by the elements described.

Such devices are permanently located in rooms in which raising of temperature above a predetermined value must be controlled to lessen fire hazard.

To control the temperature in a haystack or a similar material the device provided with a tapered element (Fig. 1) is inserted into such stack or material.

In practice the elements preferably have a length of 1 to 2 metres.

What I claim is:

, l. A raised temperature responsive electric circuit control device, comprising a tubular first conductor, a second conductor disposed within said first conductor having a spring-like portion tending toward said rst conductor, a pair of tension, and further including means` forming an 15" operative connection for a second device,

4. A device as claimed in claim 31, fiurther including at least a second device placed end to end in relation to said rst device having an extending second conductor making contact with the extended end of the second conductor of said rst device, said connection forming means connecting said respective rst conductors.

PAUL BAERTL.

REFERENCES CITED The following references are of record in the o nle of this' patent:

UNITED STATES PATENTS Number Name Date 672,266 Gardner Apr. 16, 1901 1,934,531 Guettler Nov. 7, 1933 FOREIGN PATENTS )Sl'njrilgeifr Country Date 485,121 Great Britain May 16, 1938 

